Evaluating a CRISPR-based sterile male for Drosophila suzukii (Diptera: Drosophilidae) control

Spotted-wing drosophila (SWD), Drosophila suzukii Matsumura, is a serious invasive pest of small fruits. The novel precision-guided Sterile Insect Technology (pgSIT) uses CRISPR technology to simultaneously produce sterile males and eliminate female offspring. Testing their performance in the laboratory is required before field testing is permitted. We evaluated pgSIT males with wild males regarding suppressing infestation and survivorship. In large cage trials in the laboratory, a 5:1 ratio of sterile to wild males led to a 35% or 41% reduction in offspring, and a 10:1 ratio led to 52% reduction. This indicates that sterile males were mating with wild females when wild males were present. In survivorship trials, median longevity was 1 d shorter among sterile males than wild males kept in large, ventilated cages. Finally, we performed predator feeding assays to address regulatory concerns of pgSIT technology. Green lacewing larvae, Chrysoperla rufilabris, that fed on wild or pgSIT SWD larvae developed similarly into pupae and adults. While pgSIT flies would not be present in the field at the larval stage, this test revealed no discernible impacts when predators fed on it. Rather, pgSIT males would be delivered in release boxes at the pupal stage. We found that SWD pupae, wild or sterile, were not a good food source for lacewing larvae to complete development. Given the results, further field research is warranted to test the efficacy of these sterile male SWD.